Seac Jack

The Jack is a complete and reliable freediving watch computer, developed by SEAC for the most demanding spearfisherman and freediver… but that’s not all, it encompasses a SCUBA mode as well. With a special freediving algorithm, the Jack helps reducing the risk of Taravana and Hemopthysis conditions.

The Jack is your best buddy, not only when immersed, but also for your outdoor and fitness activities via its unique features.
A lightweight techno-polymer and elastomer design, user-friendly four button intuitive menu, and a graphic LCD display, makes this computer your everyday watch companion.

Hemoptysis and Taravana function
Let's review briefly what these diseases. The Hemoptysis is technically "the emission of blood from the respiratory tract" and when it comes to spearfishing/freediving, it typically indicates the presence of a pulmonary edema. In practice: presence of blood in the lungs.
What is the cause of hemoptysis and Edema? Our lungs are crossed by a multitude of blood vessels ( "pulmonary capillaries") particularly sprayed with blood. To explain such a phenomenon in very poor words, pretend capillaries are muscles. A muscle subjected to a sudden great stress in the absence of a prior warm up phase tends to tear itself. This is what happens with our capillaries when we dive to great depths without adequate warm up dives at smaller depths, this causes the presence of blood in the lungs. To reduce the risk of pulmonary edema the JACK suggests how many warm up dives you need to do and the relevant depth in relation to the target depth you can set (in the OEDEMA function).
In the example the edema value is set to 32mt. The computer will then suggest what depths is recommended to reach with the three "warm up" dives before you dive to 32mt, to reduce the risk of pulmonary edema and subsequent hemoptysis.

The Taravana ( "madness" in Polynesian) is instead a disease whose prevention is increasingly considered both by freedivers and fishermen. The symptoms of this syndrome are comparable to severe MDD (decompression sickness) during SCUBA diving and involves disorders in speech, walking, and in severe cases seizure disorders up to coma. Hyperbaric medicine is not unanimous in identifying the underlying causes of the syndrome, however the recognized factors that increase the risk of Taravana are:
• Long stays at great depth with repeated dives (long sessions 2-4 hours) typical of spearo’s activity, in the absence of an adequate recovery time at the surface.
• Exposure to great depth in the absence of an adequate recovery time at the surface. (Typical of pure freedivers)
• Hypoxia (Insufficient presence of oxygen in the body)
• Dehydration.
The Computer after each dive will suggest the minimum "Recovery Time" (RECOVERY) before you face the following dive. The recovery time is calculated on the basis of the depth, duration and (if the MULTI function is set active) compliance of the recommended recovery time of the previous dive (if you didn’t follow the surface recovery time recommendations after the previous dive, the jack will suggest a longer recovery). Once the recommended recovery time is respected the computer no longer highlights it and continues to display the actual surface time. Based on the number of performed dives, their duration and depth, the computer display the HYDRATE alarm to remind diver to hydrate (even if the need is not felt).

On the market there are no other computers with similar functions, in most cases the other computers include the simple multiplication of the time of the dive (set manually by the user, eg. Time of dive multiplied by 1.5 times by 2.5 times, etc. ) or a manual timer, see comparison chart. According to medical and scientific literature there are multiple theories about the possible causes of Taravana and the factors that contribute to increase the risk, therefore, the algorithm of which is provided is based on the mathematical merging of three factors: 1.Nitrogen saturation, 2.Dehydratation and 3. hypoxy.
1. Nitrogen saturation: Calculated using the emiperiods of Buhlmann ZHL-16B (formerly used for scuba) for every single dive: Dive Time; depth; descent speed; ascent speed; Shape of the dive ( "U" or "V").
2. Dehydration: dive depth; dive time; Number of performed dives;
3. Hypoxia: dive depth; dive duration;
Toghether with these "fundamental factors" there are others such as the respect of the recommended recovery time in the previous dive (Single mode) or in all previous dives (Multi Mode) and the level of conservatism set (T Level). By using all of these factors, the algorithm generates the recommended recovery time to reduce the risk of Taravana and suggests when it is time to hydrate.

Alarm function
In addition to the important functions just presented, what makes this computer a very attractive product to all spearos and freedivers is the possibility to customize the alarm setting. The computer allows you to set audible alarms based on time or on depth at each dive. There are 4 different alarm modes: FIXED, STEP, TIME and OFF.
Alarm: FIXED
audible alarm at the achievement of three "targets" previously set by the user. For example Alarm 1 to 10 meters; Alarm 2 to 20 meters; Alarm 3 to 35 meters. In FIXED mode, you can set your computer to sound the alarm to the desired depth only when going down or only when going up or both. You can also set an audible alarm when you exceed a set dive time (Eg. 3:00 minutes).
Alarm: STEP
audible alarm every "X" meters. For example Alarm1 to 5m; Alarm2 to 10m; Alarm3 to 15 mt; Alarm4 to 20 meters; Alarm 5 to 25 m; etc. when the mode STEP is activated the alarm is audible only during the descent and as with the FIXED mode, you can set an additional acoustic signal when you exceed the dive time set (Eg. 3:00 minutes).
Alarm: TIME
Only the dive time acoustic signal is active.
Alarm: OFF
No active alarm.

Outdoor functions
Finally, in addition to the functions described until now that are useful only in the water JACK is equipped with other features that make it useful for activities commonly carried out of the water. It’s clearly a watch so it provides you with the exact time and it is equipped with compass, barometer, altimeter, weather forecast, thermometer (air), pedometer (which shows the distance traveled, speed and calories burned), stopwatch, moon phases (ideal for tides ).